Glycoprotein D (gD) is an essential envelope protein from the herpes simplex virus (HSV). The two strains of HSV, HSV-1 and HSV-2, both contain gD, and gD-1 and gD-2 are 80% homologous in sequence. Truncated versions of the two proteins have been cloned in a baculovirus expression system. The proteins have all the amino acids necessary for function including in vitro assays, have the proper conformation, and are soluble since they are truncated at amino acid 306 prior to the hydrophobic transmembrane region. They are called gD-1(306t) and gD-2(306t). Two additional mutants of gD-1(306t) have been cloned and expressed. Whereas the wild-type has three N-linked carbohydrates, gD-1(TAAt) has only one and gD-1(QAAt) has none. Both proteins have the proper conformation and function in in vitro assays. The protein gD-1(306t) appears dimeric by gel filtration data. Preliminary mass analysis in the STEM agrees with this. Additional mass measurements on all four of these proteins are underway to determine if they are all dimers.